65),
he wrote to Hooker: "A man told me the other day of, as I thought, a
splendid instance--and splendid it was, for according to his evidence
the seed came up alive out of the lower part of the London Clay! I
disgusted him by telling him that palms ought to have come up."

In the "Gardeners' Chronicle," 1855, page 758, appeared a notice (half
a column in length) by Darwin on the "Vitality of Seeds." The facts
related refer to the "Sand-walk" at Down; the wood was planted in 1846
on a piece of pasture land laid down as grass in 1840. In 1855, on the
soil being dug in several places, Charlock (Brassica sinapistrum) sprang
up freely. The subject continued to interest him, and we find a note
dated July 2nd, 1874, in which Darwin recorded that forty-six plants
of Charlock sprang up in that year over a space (14 x 7 feet) which had
been dug to a considerable depth. In the course of the article in the
"Gardeners' Chronicle," Darwin remarks: "The power in seeds of retaining
their vitality when buried in damp soil may well be an element in
preserving the species, and therefore seeds may be specially endowed
with this capacity; whereas the power of retaining vitality in a dry
artificial condition must be an indirect, and in one sense accidental,
quality in seeds of little or no use to the species."

The point of view expressed in the letter to Lyell above given is of
interest in connection with the research of Horace Brown and F. Escombe
(577/3. "Proc. Roy. Soc." Volume LXII., page 160.) on the remarkable
power possessed by dry seeds of resistance to the temperature of liquid
air. The point of the experiment is that life continues at a temperature
"below that at which ordinary chemical reactions take place." A still
more striking demonstration of the fact has been made by Thiselton-Dyer
and Dewar who employed liquid hydrogen as a refrigerant. (577/4. Read
before the British Association (Dover), 1899, and published in the
"Comptes rendus," 1899, and in the "Proc. R. Soc." LXV., page 361,
1899.) The connection between these facts and the dormancy of buried
seeds is only indirect; but inasmuch as the experiment proves the
possibility of life surviving a period in which no ordinary chemical
change occurs, it is clear that they help one to believe in greatly
prolonged dormancy in conditions which tend to check metabolism. For a
discussion of the bearing of their results on the life-problem, and for
the literature of the subject, r